Chapter 11 Heating the Atmosphere
Weather and Climate
Weather Weather is over a short period of time Constantly changing
Climate Climate is over a long period of time Generalized, composite of weather
Weather and Climate
Elements of weather and climate Properties that are measured regularly Most important elements
Temperature Humidity Cloudiness Precipitation Air Pressure Winds speed and direction
Origin of the AtmosphereOutgassing occurred from volcanoes - Original composition of atmosphere is predicted to be similar to composition of present day volcanoes
80% water vapor, 10% CO2, and <1-2% nitrogen
Origin of the Atmosphere
Changes over time
1. Water vapor condensed to form liquid water
2. CO2 became locked up in rocks
3. Nitrogen, which is chemically inactive, increased
4. When plants evolved oxygen became more abundant
5. Variations - CO2 changes can cause climate changes
Current Composition of the Atmosphere
Air is a mixture of discrete gases Major permanent components of
clean, dry air Nitrogen (N)—78% Oxygen (O2)—21%
Argon and other gases Carbon dioxide (CO2)—0.036%—
absorbs heat energy from Earth
Composition of Dry Air
Composition of the Atmosphere
Major Variable components of air
Water vapor Aerosols Ozone CO2
Composition of the Atmosphere
Importance of Variable components Water vapor
Up to about 4% of the air's volume Forms clouds and precipitation Greenhouse gas (Absorbs heat energy from Earth)
Composition of the Atmosphere
AerosolsTiny solid and liquid particles Water vapor can condense on solidsReflect sunlightHelp color sunrise and sunset
Major Variable components of air
Composition of the Atmosphere
Ozone Three atoms of oxygen (O3)
Distribution not uniform Concentrated between 10 to 50 kilometers above the surface (Stratosphere)Absorbs harmful UV radiation Human activity is depleting ozone by adding chlorofluorocarbons (CFCs)
Major Variable components of air
Composition of the AtmosphereOzone Depletion
Atmospheric Pressure
Pressure changes Pressure is the weight of the air above Average sea level pressure
Slightly more than 1000 millibars About 14.7 pounds per square inch
Pressure decreases with altitude One half of the atmosphere is below 3.5
miles (5.6 km) Ninety percent of the atmosphere is below
10 miles (16 km)
Atmospheric Pressure Measurement of Air Pressure
Atmospheric Pressure
Measurement of Air Pressure
Atmospheric Pressure Variation
with Altitude
Heat and Temperature
Heat is the total kinetic energy of the atoms or molecules that make up the substance
Temperature is the average of the kinetic energy of the individual atoms or molecules that make up the substance
Thermal Structure of the Atmosphere
Thermal Structure of the AtmosphereAtmospheric layers based on
Temperature Troposphere
Bottom layer Temperature decreases with altitude—Called
the environmental lapse rate 6.5˚C per kilometer (average) 3.5˚F per 1000 feet (average)
Thickness varies—Average height is about 12 km
Outer boundary is named the tropopause
Thermal Structure of the Atmosphere
Structure of the Atmosphere
Atmospheric layers based on temperature Stratosphere
About 12 km to 50 km Temperature increases at top (>20 km) Contains most of the atmosphere’s ozone Outer boundary is named the stratopause >99% of earth atmosphere is below
stratopause
Thermal Structure of the Atmosphere
Structure of the Atmosphere
Atmospheric layers based on temperature Mesosphere
About 50 km to 80 km Temperature decreases – coldest portion of
atmosphere Outer boundary is named the mesopause Contains ionosphere- a region of particles
charged by the suns energy
Thermal Structure of the Atmosphere
Structure of the Atmosphere
Atmospheric layers based on temperature Thermosphere
No well-defined upper limit Fraction of atmosphere's mass
Gases moving at high speeds
Composition of the Atmosphere
Homosphere – composition of air is well mixed (<80 km)
Heterosphere – composition of air is segregated >80 km)
Earth–Sun Relations Earth motions
Rotates on its axis – 23½ Revolves around the Sun every 365¼ days The earths orbit is elliptical – the erath is 147
million km from the sun on January 3 and 152 million kms on July 4
Average 150km from earth
Earth–Sun Relations
Seasons are a result of :1) Changing Sun angle
2) Changing length of daylight
June 21 December 21
Relationship of Sun Angle and Intensity of Solar Radiation
Earth–Sun Relations
Seasons are a result of :1) Changing Sun angle
2) Changing length of daylight
June 21 December 21
Earth–Sun Relations Seasons
Caused by Earth's changing orientation to the Sun Axis is inclined 23½° Axis is always pointed in the same direction
Special days (Northern Hemisphere) Summer solstice
June 21–22 Sun's vertical rays are located at the
tropic of Cancer (23½° N latitude)
Earth–Sun relations Seasons
Special days (Northern Hemisphere) Winter solstice
December 21–22 Sun's vertical rays are located at the
tropic of Capricorn (23½° S latitude) Autumnal equinox
September 22–23 Sun's vertical rays are located at the
equator (0° latitude)
Earth–Sun relations Seasons
Special days (Northern Hemisphere) Spring equinox
March 21–22 Sun's vertical rays are located at the
equator (0° latitude)
Earth–Sun Relationships
Earth-Sun Relations
Atmospheric Heating
The Second Law of Thermodynamics states that:
Heat is always transferred from warmer to cooler objects
Atmospheric Heating
Mechanisms of heat transfer Conduction through molecular activity
Convection Mass movement within a substance
Radiation (electromagnetic radiation) Needs no material to transfer heat Velocity: 300,000 kilometers (186,000
miles) per second in a vacuum
Mechanisms of Heat Transfer
Atmospheric Heating
Mechanisms of heat transfer Radiation (electromagnetic radiation)
Consists of different wavelengths Gamma (very short waves) X-rays Ultraviolet (UV) Visible Infrared Microwaves and radio waves
The Electromagnetic Spectrum
Atmospheric Heating
Mechanisms of heat transfer Radiation (electromagnetic radiation)
Governed by basic laws Hotter objects radiate more total energy
per unit area than do cooler objects The hotter the radiating body, the shorter
the wavelength of maximum radiation Objects that are good absorbers of
radiation are good emitters as well
Atmospheric Heating
Incoming solar radiation Atmosphere is largely transparent to
incoming solar radiation Most visible radiation reaches the
surface About 50% absorbed at Earth's surface
Average Distribution of Incoming Solar Radiation
Atmospheric Heating Atmospheric effects
Reflection—Albedo (percent reflected) Scattering Absorption
Atmospheric Heating Reflection—Albedo (percent reflected)
Atmospheric HeatingScattering
Atmospheric Heating
Radiation from Earth's surface Earth re-radiates radiation (terrestrial
radiation) at the longer wavelengths Longer wavelength terrestrial radiation
is absorbed by Carbon dioxide and water vapor Lower atmosphere is heated from Earth's
surface
Heating of the atmosphere is termed the greenhouse effect
Heating of the Atmosphere
Global Warming
Controls of Global Temperatures
Temperature variations Receipt of solar radiation is the most
important control Other important controls
Differential heating of land and water Land heats more rapidly than water Land gets hotter than water Land cools faster than water Land gets cooler than water
Controls of Temperature
Other important controls Altitude Geographic position Cloud cover Albedo
Maritime Influence on Temperature
Altitude Influence on Temperature
Geographic Influence on Temperature
Clouds Reduce the Daily
Temperature Range
End of Chapter 11